Conventional mortar weapons (also referred to as mortars) and mortar ammunition has looked pretty much the same since the days of the First World War. Conventional mortars are not especially suited to mounting on vehicles. Where installed on vehicles extensive manual handling is required, both of the mortar by redeploying vehicles and of the shell by changing the number of charges. It is necessary either to sacrifice armour protection and to load the mortar manually from open hatches, or to design complicated loading apparatus which moves shells from the inside of the vehicle to the muzzle of the mortar barrel. A further problem is that the shell lies loosely in the barrel, which means that the mortar can only be fired with a high angle of elevation. If attempts are made to tip the mortar, that is to say to lower the barrel below a certain angle of elevation, there is a great risk that the shell will shift or slide out of the barrel.
Devices to prevent the shell shifting prior to firing, for example when adjusting the angle of elevation of the barrel, have long been known. GB 2 260 390 A discloses and describes a device for locking a shell. The locking device consists of a locking plate and snap fastening. The locking device is fixed to the rear part of the shell, behind the fins of the shell, following which the shell is rammed home into the weapon. The locking plate is disc-shaped and has an outside diameter greater than the inside diameter of the barrel. When ramming the shell home in the barrel the locking plate will be rammed home against a shoulder, which is formed due to the fact that the breech opening diameter of the barrel has been made greater than the remaining diameter of the barrel. The shell is thereby fixed in a specific position inside the barrel. In firing, the locking element is torn off the shell and remains in the barrel. Before the mortar can be reloaded the locking element must be taken care of, either manually or with the aid of a special tool. Locking elements therefore entail a further component that has to be handled as part of the weapon logistics system.
The component must be transported, handled by the ammunition handling system, fitted to the shell, removed from the barrel before the next round can be rammed home, sorted out as scrap and assigned for destruction or reuse. Due to the high pressure and temperature that occur in firing, there is often a risk of the locking element being burned onto or otherwise adhering to the to the breech opening, which in the worst case can lead to fracture of the barrel. In order to cope with the burnt-on component or residues of components, special tools are required, which represent extra equipment in the weapons system. Handling the locking element therefore entails a slower and more complicated weapons system, in which the risk of barrel fracture is great owing to the locking element.